Poly(arylene thioether-ketone) fibers and production process thereof

ABSTRACT

Disclosed herein are poly(arylene thioether-ketone) fibers obtained by melt-spinning a thermoplastic material which comprises 100 parts by weight of a melt-stable poly(arylene thioether-ketone) (PTK) and optionally, up to 50 parts by weight of at least one of thermoplastic resins. The PTK has predominant recurring units of the formula ##STR1## wherein the --CO-- and --S-- are in the para position to each other, and has a melting point, Tm of 310°-380° C., a residual melt crystallization enthalpy, ΔHmc (420° C./10 min) of at least 10 J/g, a melt crystallization temperature, Tmc (420° C./10 min) of at least 210° C., and a reduced viscosity of 0.3-2 dl/g as determined by viscosity measurement at 25° C. and a polymer concentration of 0.5 g/dl in 98 percent by weight sulfuric acid. The PTK fibers of this invention have high heat resistance and strength.

This is a division of application Ser. No. 194,014, filed May 12, 1988.

FIELD OF THE INVENTION

This invention relates to fibers obtained by melt-spinning athermoplastic material composed principally of a melt-stablepoly(arylene thioetherketone) (hereinafter abbreviated as "PTK") havingpredominant recurring units of the formula ##STR2## in which the--CO--and --S--are in the para position to each other, and morespecifically to PTK fibers having high heat resistance and strength,which are obtained by melt-spinning a thermoplastic material composed ofthe melt-stable PTK and optionally, at least one of other thermoplasticresins and/or one or more of various fillers.

BACKGROUND OF THE INVENTION

With the advance of weight-, thickness- and length-reducing technologyin the field of the electronic and electric industry and with the recentadvancement of weight-reducing technology in the fields of theautomobile, aircraft and space industries, there has been a strongdemand for crystalline thermoplastic resins having heat resistance ofabout 300° C. or higher and permitting easy melt processing in recentyears.

As crystalline, heat-resistant, thermoplastic resins developed to date,there are, for example, poly(butylene terephthalate), polyacetal,poly(p-phenylene thioether), etc. These resins are however unable tomeet the recent requirement level for heat resistance.

Polyether ether ketones (hereinafter abbreviated as "PEEKs") andpolyether ketones (hereinafter abbreviated as "PEKs") have recently beendeveloped as heat-resistant resins having a melting point of about 300°C. or higher. These resins are crystalline thermoplastic resins. It hastherefore been known that conventional melt processing techniques suchas extrusion, injection molding, melt spinning, blow molding andlaminate molding can be applied to easily form them into various moldedor formed articles such as extruded products, injection-molded products,fibers and films. These resins however use expensivefluorine-substituted aromatic compounds such as4,4'-difluorobenzophenone as their raw materials. Limitations are thussaid to exist to the reduction of their costs. It is also pointed outthat these resins involve a problem in expanding their consumption.

Based on an assumption that PTKs could be promising candidates forheat-resistant thermoplastic resins like PEEKs and PEKs owing to theirsimilarity in chemical structure, PTKs have been studied to some extentto date. There are some disclosure on PTKs, for example, in JapanesePatent Laid-Open No. 58435/1985 (hereinafter abbreviated as "PublicationA"), German Offenlegungsschrift 34 05 523Al (hereinafter abbreviated as"Publication B"), Japanese Patent Laid-Open No. 104126/1985 (hereinafterabbreviated as "Publication C"), Japanese Patent Laid-Open No.13347/1972 (hereinafter abbreviated as "Publication D"), Indian J.Chem., 21A, 501-502 (May, 1982) (hereinafter abbreviated as "PublicationE"), and Japanese Patent Laid-Open No. 221229/1986 (hereinafterabbreviated as "Publication F").

Regarding the PTKs described in the above publications, neither moldingnor forming has however succeeded to date in accordance withconventional melt processing techniques. Incidentally, the term"conventional melt processing techniques" as used herein means usualmelt processing techniques for thermoplastic resins, such as extrusion,injection molding, melt spinning, blow molding, laminate molding, etc.

The unsuccessful molding or forming of PTKs by conventional meltprocessing techniques is believed to be attributed to the poor meltstability of the prior art PTKs, which tended to lose theircrystallinity or to undergo crosslinking and/or carbonization, resultingin a rapid increase in melt viscosity, upon their melt processing.

It was attempted to produce some molded or formed products inPublications A and B. Since the PTKs had poor melt stability, certainspecified types of molded or formed products were only obtained by aspecial molding or forming process, where PTKs were used only as a sortof binder, being impregnated into a great deal of reinforcing fibers ofmain structural materials and molded or formed under pressure.

Since the conventional PTKs are all insufficient in melt stability asdescribed above, it has been unable to obtain formed products such asfibers even from compositions of the PTKs with another thermoplasticresin and a filler, to say nothing of the PTKs alone, by applyingconventional melt processing techniques.

OBJECTS AND SUMMARY OF THE INVENTION

An object of this invention is to overcome the above-mentioned drawbacksof the prior art and hence to provide fibers by melt-spinning amelt-stable PTK which permits easy application of a conventional meltprocessing technique.

Another object of this invention is to provide fibers, which have highheat resistance and strength, by melt-spinning a thermoplastic materialwhich comprises a melt-stable PTK alone or a composition of amelt-stable PTK and at least one of thermoplastic resins.

A further object of this invention is to produce PTK fiberseconomically.

The present inventors started an investigation with a view toward usingeconomical dichlorobenzophenone and/or dibromobenzophenone as a rawmaterial for PTKs without employing any expensive fluorine-substitutedaromatic compound. In addition, a polymerization process was designed inan attempt to conduct polymerization by increasing the water content inthe polymerization system to an extremely high level compared toprocesses reported previously, adding a polymerization aid and suitablycontrolling the profile of the polymerization temperature. As a result,high molecular-weight PTKs were obtained economically. The PTKs obtainedby the above process were however still dissatisfactory in meltstability.

Thus, the present inventors made further improvements in thepolymerization process. It was then revealed that melt-stable PTKs,which permitted the application of conventional melt processingtechniques, could be obtained by conducting polymerization withoutaddition of any polymerization aid while paying attention to theselection of a charge ratio of monomers, the shortening of thepolymerization time at high temperatures, the selection of a materialfor a polymerization reactor, etc. and if necessary, by conducting astabilization treatment in a final stage of the polymerization. It wasalso found that PTK fibers having high heat resistance and strengthcould be obtained easily from a thermoplastic material composedprincipally of the melt-stable PTKs by general melt-processingtechniques.

These findings have led to the completion of the present invention.

In one aspect of this invention, there is thus provided poly(arylenethioether-ketone) fibers obtained by melt-spinning a thermoplasticmaterial which comprises:

(A) 100 parts by weight of a melt-stable poly(arylene thioether-ketone)having predominant recurring units of the formula ##STR3## wherein the--CO--and --S--are in the para position to each other, and having thefollowing physical properties (a)-(c):

(a) melting point, Tm being 310-380° C.;

(b) residual melt crystallization enthalpy, ΔHmc (420° C./10 min) beingat least 10 J/g, and melt crystallization temperature, Tmc (420° C./10min) being at least 210° C., wherein ΔHmc (420° C./10 min) and Tmc (420°C./10 min) are determined by a differential scanning calorimeter(hereinafter abbreviated as "DSC") at a cooling rate of 10° C./min,after the poly(arylene thioether-ketone) is held at 50° C. for 5 minutesin an inert gas atmosphere, heated to 420° C. at a rate of 75° C./minand then held for 10 minutes at 420° C.; and

(c) reduced viscosity being 0.3-2 dl/g as determined by viscositymeasurement at 25° C. and a polymer concentration of 0.5 g/dl in 98percent by weight sulfuric acid; and optionally,

(B) up to 50 parts by weight of at least one of thermoplastic resins.

In another aspect of this invention, there is also provided a processfor the production of poly(arylene thioether-ketone) fibers, whichcomprises melt-extruding the above-described thermoplastic material atan extrusion temperature of 320-430° C. through a spinneret, stretchingthe resultant fibers to a draw ratio of from 1.2:1 to 8:1 within atemperature range of 120-200° C., and then heat setting thethus-stretched fibers at 130-370° C. for 0.1-1,000 seconds.

Owing to the use of the PTK having melt stability, the present inventionhas made it possible for the first time to obtain PTK fibers having highheat resistance and strength from the PTK or a thermoplastic resincomposition composed principally of the PTK in accordance with amelt-spinning technique.

DETAILED DESCRIPTION OF THE INVENTION

Features of the present invention will hereinafter be described indetail.

Chemical Structure of PTKs

The melt stable PTKs according to the present invention are poly(arylenethioether-ketones) (PTKs) having predominant recurring units of theformula ##STR4## wherein the --CO--and --S--are in the para position toeach other. In order to be heatresistant polymers comparable with PEEKsand PEKs, the PTKs of this invention may preferably contain, as a mainconstituent, the above recurring units in a proportion greater than 50wt.%, more preferably, of 60 wt.% or higher, most preferably, of 70 wt.%or higher. If the proportion of the recurring units is 50 wt.% or less,there is a potential problem that the crystallinity of the polymer isreduced and its heat resistance is reduced correspondingly.

Exemplary recurring units other than the above recurring units mayinclude: ##STR5##

It is desirable that the melt stable PTKs of this invention are uncuredpolymers, especially, uncured linear polymers The term "cure" as usedherein means a molecular-weight increasing treatment for a polymer by amethod other than a usual polycondensation reaction, for example, by acrosslinking, branching or molecular-chain extending reaction,particularly, a molecular-weight increasing treatment by ahigh-temperature heat treatment or the like. In general, "curing" causesa PTK to lose or decrease its melt stability and crystallinity. Curingtherefore makes it difficult to employ conventional melt processing of aPTK. Even if fibers are obtained, they tend to have a low density andreduced crystallinity, in other words, may not be regarded as"heat-resistant fibers" substantially. Curing is hence not preferred.

However, PTKs having a partially crosslinked and/or branched structureto such an extent still allowing the application of conventional meltprocessing techniques are still embraced in the present invention. Forexample, PTKs obtained by conducting polymerization in the presence of asmall amount of a crosslinking agent (e.g., polychlorobenzophenone,polybromobenzophenone or the like) and PTKs subjected to mild curing canbe regarded as melt-stable PTKs useful for fibers according to thisinvention.

Physical Properties of PTKs

The melt stable PTKs useful in the practice of this invention have thefollowing physical properties.

(a) As indices of the characteristics of heat-resistant polymers, theirmelting points, Tm range from 310 to 380° C.

(b) As indices of the melt stability of polymers to which conventionalmelt processing techniques can be applied, their residual meltcrystallization enthalpies, ΔHmc (420° C./10 min) are at least 10 J/g,and their melt crystallization temperatures, Tmc (420° C./10 min) are atleast 210° C.

(c) In the case of extrusion products such as fibers, their shaping isdifficult due to drawdown or the like upon melt forming unless themolecular weight is sufficiently high. They should have a sufficientlyhigh molecular weight. As indices of the molecular weights of thepolymers, their reduced viscosities η_(red) should be within the rangeof 0.3-2 dl/g.

In the present invention, each reduced viscosity η_(red) is expressed bya value as measured at 25° C. and a polymer concentration of 0.5 g/dl in98 percent by weight sulfuric acid as a solvent.

(d) As indices of the characteristics of highly-crystalline polymers,the polymers have a density of at least 1.34 g/cm³ at 25° C whenannealed at 280° C. for 30 minutes.

Next, the physical properties of the melt stable PTKs useful in thepractice of this invention will be described in detail.

(1) Heat resistance:

The melting point, Tm of a polymer serves as an index of the heatresistance of the polymer.

The PTKs useful in the practice of this invention have a melting point,Tm of 310-380° C., preferably 320°-375° C., more preferably 330°-370° C.Those having a melting point, Tm lower than 310° C. are insufficient inheat resistance as heat-resistant resins comparable with PEEKs and PEKs.On the other hand, it is difficult to perform the melt processing ofthose having a melting point, Tm higher than 380° C. withoutdecomposition. Such an excessively low or high melting point isundesired.

(2) Melt stability:

The greatest feature of the PTKs useful in the practice of thisinvention resides in that they have melt stability sufficient to permitthe application of conventional melt processing techniques.

All the conventional PTKs have low melt stability and tend to lose theircrystallinity or to undergo crosslinking or carbonization, resulting ina rapid increase in melt viscosity, upon their melt processing.

It is hence possible to obtain an index of the melt processability of aPTK by investigating the residual crystallinity of the PTK after holdingit at an elevated temperature of its melt processing temperature orhigher for a predetermined period of time. The residual crystallinitycan be evaluated quantitatively in terms of melt crystallizationenthalpy. Specifically, the residual melt crystallization enthalpy, ΔHmc(420° C./10 min) and its melt crystallization temperature, Tmc (420°C./10 min) of the PTK which are determined by a DSC at a cooling rate of10° C. after the PTK is held at 50° C. for 5 minutes in an inert gasatmosphere, heated to 420° C. at a rate of 75° C./min and then held for10 minutes at 420° C., can be used as measures of its melt stability. Inthe case of a PTK having poor melt stability, it undergoes crosslinkingor the like at the above high temperature condition of 420° C. and losesits crystallinity substantially.

The melt stable PTKs useful in the practice of this invention arepolymers whose residual melt crystallization enthalpies, ΔHmc (420°C./10 min) are preferably at least 10 J/g, more preferably at least 15J/g, most preferably at least 20 J/g and whose melt crystallizationtemperatures, Tmc (420° C./10 min) are preferably at least 210° C., morepreferably at least 220° C., most preferably at least 230° C.

A PTK, whose ΔHmc (420° C./10 min) is smaller than 10 J/g or whose Tmc(420° C./10 min) is lower than 210° C., tends to lose its crystallinityor to induce a melt viscosity increase upon its melt processing, so thatdifficulties are encountered upon application of conventional meltprocessing techniques such as melt spinning.

(3) Molecular weight:

The solution viscosity, for example, reduced viscosity η_(red) of apolymer can be used as an index of its molecular weight.

When a PTK or a PTK composition is subjected to melt spinning, drawdownor the like may occur as a problem upon its melt processing.

Therefore, the molecular weight which is correlated directly to the meltviscosity of the PTK is also an important factor for its meltprocessability.

In order to apply conventional melt processing techniques, highmolecular-weight PTKs whose reduced viscosities, η_(red) are preferably0.3-2 dl/g, more preferably 0.5-2 dl/g, are desired. Since a PTK whoseη_(red) is lower than 0.3 dl/g has a low melt viscosity and hightendency of drawdown, it is difficult to apply conventional meltprocessing techniques such as melt spinning. Further, fibers from such aPTK are insufficient in mechanical properties.

On the other hand, a PTK whose η_(red) exceeds 2 dl/g is very difficultin production and process.

(4) Crystallinity:

As an index of the crystallinity of a polymer, its density is used.

The PTKs useful in the practice of this invention are desirably polymerswhose densities (at 25° C.) are preferably at least 1.34 g/cm³, morepreferably at least 1.35 g/cm³ when measured in a crystallized form byannealing them at 280° C. for 30 minutes. Those having a density lowerthan 1.34 g/cm³ have potential problems that they may have lowcrystallinity and hence insufficient heat resistance and mechanicalproperties of resulting fibers may also be insufficient.

In particular, PTKs crosslinked to a high degree (e.g., the PTKsdescribed in Publication A) have been reduced in crystallinity and theirdensities are generally far lower than 1.34 g/cm³.

Production Process of PTKs

The melt stable PTKs useful in the practice of this invention can eachbe produced, for example, by subjecting an alkali metal sulfide and adihalogenated aromatic compound, preferably, dichlorobenzophenone and/ordibromobenzophenone to dehalogenation and sulfuration, for a shortperiod of time, in the substantial absence of a polymerization aid (asalt of a carboxylic acid, or the like), in an aprotic polar organicsolvent, preferably, an organic amide solvent (including a carbamicamide or the like) and in a system having a water content far highercompared with conventionally-reported polymerization processes whilecontrolling the temperature profile suitably, and if necessary, bychoosing the material of a reactor suitably.

Namely, the melt stable PTKs useful in the practice of this inventioncan each be produced suitably by polymerizing an alkali metal sulfideand a dihalogenated aromatic compound consisting principally of4,4'-dichlorobenzophenone and/or 4,4'-dibromobenzophenone bydehalogenation and sulfuration under the following conditions (a)-(c) inan organic amide solvent.

(a) ratio of the water content to the amount of the charged organicamide: 2.5-15 (mole/kg);

(b) ratio of the amount of the charged dihalogenated aromatic compoundto the amount of the charged alkali metal sulfide: 0.95-1.2 (mole/mole);and

(c) reaction temperature: 60-300° C. with a proviso that the reactiontime at 210° C. and higher is within 10 hours.

The melt stable PTKs can be obtained more suitably when a reactor atleast a portion of which, said portion being brought into contact withthe reaction mixture, is made of a corrosion-resistant material such astitanium material.

Optionally, at least one halogen-substituted aromatic compound having atleast one substituent group having electron-withdrawing property atleast equal to --CO--group (preferably, 4,4'-dichlorobenzophenone and/or4,4'-dibromobenzophenone employed as a monomer) may be added and reacted(as a stabilization treatment in a final stage of the polymerization) soas to obtain PTKs improved still further in melt stability.

The melt stable PTKs employed in the present invention may preferably beuncured polymers as described above. They may however be PTKs in which acrosslinked structure and/or a branched structure has been incorporatedto a certain minor extent. In order to obtain a PTK with a branched orcrosslinked structure introduced therein, it is preferable to have apolyhalogenated compound, especially, a polyhalogenated benzophenonehaving at least three halogen atoms exist as a crosslinking agent in thepolymerization reaction system in such an amount that the charge ratioof the monomeric dihalogenated aromatic compound to the polyhalogenatedbenzophenone ranges from 100/0 to 95/5 (mole/mole). If the amount of thecharged polyhalogenated benzophenone is too much, physical properties ofthe resulting PTK, such as their melt processability, density andcrystallinity, will be reduced. It is hence not preferable to chargesuch a polyhalogenated benzophenone too much.

Thermoplastic Resin

The thermoplastic material used as a raw material for the melt-spinningin this invention may be composed of the melt-stable PTK alone. In viewof processability, physical properties, economy and the like, it mayalso be a resin composition obtained by mixing at least one of otherthermoplastic resins in a proportion of 0-50 parts by weight, preferably0-40 parts by weight, and more preferably 0-30 parts by weight, all, per100 parts by weight of the PTK. It is not preferable to add thethermoplastic resin in any amount greater than 50 parts by weight,because such a high proportion results in fibers of reduced heatresistance and heat shrinkage resistance.

As exemplary thermoplastic resins useful in the present invention, maybe mentioned resins such as poly(arylene thioethers), PEEKs and PEKs,polyamides (including Aramids), polyamideimides, polyesters (includingaromatic polyesters and liquid crystalline polyesters), polysulfones,polyether sulfones, polyether imides, polyarylenes, poly(phenyleneethers), polycarbonates, polyester carbonates, polyacetals,fluoropolymers, polyolefins, polystyrenes, polymethyl methacrylate, andABS; as well as elastomers such as fluororubbers, silicone rubbers,olefin rubbers, acrylic rubbers, polyisobutylenes (including butylrubber), hydrogenated SBR, polyamide elastomers and polyesterelastomers.

Among the above-exemplified thermoplastic resins, poly(arylenethioethers), especially, poly(arylene thioethers) having predominantrecurring units of the formula ##STR6## (hereinafter abbreviated as"PATEs"; said recurring units accounting for at least 50 wt.%) arepreferred, because the PATEs have good compatibility with the PTK andtheir blending with the PTK can provide fibers which have mechanicalproperties improved over those obtained from the PTK alone at roomtemperature and also heat resistance improved over those obtained fromthe PATEs alone and are well-balanced in heat resistance and mechanicalproperties.

Other components:

In this invention, one or more of fibrous fillers and/or inorganicfillers may be added in a proportion up to 10 parts by weight per 100parts by weight of the PTK as desired. If the proportion of the fillerexceeds 10 parts by weight, there is a potential problem that theprocessability may be deteriorated to a considerable extent and thephysical properties of the resulting fibers would be deteriorated.

As exemplary fibrous fillers usable in this invention, may be mentionedfibers such as glass fibers, carbon fibers, graphite fibers, silicafibers, alumina fibers, zirconia fibers, silicon carbide fibers andAramid fibers; as well as whiskers such as potassium titanate whiskers,calcium silicate (including wollastonite) whiskers, calcium sulfatewhiskers, carbon whiskers, silicon nitride whiskers and boron whiskers.

As exemplary inorganic fillers, may be mentioned talc, mica, kaolin,clay, silica, alumina, silica-alumina, titanium oxide, iron oxides,chromium oxide, calcium carbonate, calcium silicate, calcium phosphate,calcium sulfate, magnesium carbonate, magnesium phosphate, silicon,carbon (including carbon black), graphite, silicon nitride, molybdenumdisulfide, glass, hydrotalcite, ferrite, samarium-cobalt,neodium-iron-boron, etc., all, in a powder form.

These fibrous fillers and inorganic fillers may be used either singly orin combination.

In this invention, it is feasible to add one or more of additives suchas stabilizers, anticorrosives, lubricants, surface-roughening agents,ultraviolet absorbents, nucleating agents, mold-releasing agents,colorants, coupling agents and antistatic agents, as needed.

Production Process of Fibers

The PTK fibers of this invention can be produced by charging athermoplastic material, which is composed of the melt-stable PTK or thecomposition of the melt-stable PTK and at least one of thermoplasticresins, for example, into a spinneret-equipped extruder in the air orpreferably, in an inert gas atmosphere, extruding the thermoplasticmaterial at an extrusion temperature of 320-430° C., stretching theresultant fibers to a draw ratio of from 1.2:1 to 8:1 within atemperature range of 120-200° C., and then heat setting thethus-stretched fibers at 130-370° C. for 0.1-1,000 seconds. Uponextrusion through the spinneret, fibers are generally taken up at a drawdown ratio (the ratio of the take-up speed of spun fibers to thedischarge rate of the resin from the spinneret) of from 1:1 to 1000:1,preferably, from 5:1 to 500:1.

If the extrusion temperature from the spinneret is lower than the abovetemperature range, it is difficult to achieve smooth spinning. If it istoo high on the contrary, deterioration of the resin is induced.Extrusion temperatures outside the above range are hence not preferred.The fibers extruded from the spinneret are stretched in the solid stateand are hence oriented. The stretching is carried out at a temperaturenot higher than the melting point of the PTK, preferably, at 120-200° C.The stretching step may be performed, for example, by stretchingmelt-spun and unstretched fibers in a dry heat bath or wet heat bath ofa high temperature or on a hot plate of a high temperature. If thestretching temperature is outside the specified temperature range, endbreakages, fuzzing and/or melt bonding tends to take place. Stretchingtemperatures outside the above temperature range are hence notpreferred.

The draw ratio ranges from 1.2:1 to 8:1. Draw ratios smaller than 1.2:1are difficult to obtain high-strength fibers. On the other hand, drawratios greater than 8:1 encounter difficulties in stretching and induceend breakages and/or fuzzing. Draw ratios outside the above range aretherefore not preferred. By applying heat setting subsequent tostretching, fibers having high strength and a small heat shrinkagefactor can be obtained.

Physical Properties of Fibers

The PTK fibers of this invention generally have a fiber diameter of0.5-1,000 μm, preferably, 1-300 μm and has the following excellentphysical properties:

(a) density of PTK portions being at least 1.34 g/cm³ at 25° C.;

(b) tensile strength being at least 10 kg/mm² at 23° C. or at least 3kg/mm² at 250° C.;

(c) tensile modulus being at least 100 kg/mm² at 23° C. or at least 30kg/mm² at 250° C.;

(d) tensile elongation being at least 5% at 23° C.; and

(e) heat shrinkage (220° C./30 min) being at most 20%.

(Measurements of physical properties)

Density of PTK portions (25° C.):

Where the thermoplastic material as the raw material of the fibers iscomposed of the PTK alone, the density (25° C.) of PTK portions is thesame as the density (25° C.) of the fibers. Where the thermoplasticmaterial contains the thermoplastic resin and/or filler as a furthercomponent in addition to the PTK, a sample is separately prepared underthe same conditions for the production of the fibers by using the samethermoplastic material except for the omission of the PTK, and thedensity (25° C.) of PTK portions can be determined from the density (25°C.) of the fibers and the density (25° C.) of the sample free of thePTK. ##EQU1##

Tensile strength:

JIS-L1013 was followed (sample length: 300 mm; drawing rate: 300mm/min).

Tensile modulus:

JIS-L1013 was followed [stress (modulus of elasticity) at 1% deformation(elongation)].

Tensile elongation:

JIS-L1013 was followed. Heat shrinkage (220° C./30 min):

After aging each fiber sample at 220° C. for 30 minutes, the degree ofshrinkage of the sample was determined.

As has been described above, the PTK fibers of this invention are fibersobtained by using a melt-stable PTK having a high molecular weight of0.3-2 dl/g in terms of reduced viscosity, a density of 1.34 g/cm³ whenannealed at 280° C. for 30 minutes and a melting point, Tm of 310-380°C. The PTK fibers thus have high heat resistance and strength.

Application Fields of PTK Fibers of This Invention

Although the fibers of this invention are not used in any particularlylimited fields, industrial filters, heat-insulating materials,reinforcing fibers, insulating tapes, insulating cloths, fireproofwears, high-temperature gloves, prepreg fibers, tension members foroptical-fiber cables, etc. may be mentioned by way of example as theirspecific application fields.

ADVANTAGES OF THE INVENTION

PTK fibers having high heat resistance and strength were successfullyobtained by the present invention. PTKs according to conventionaltechniques had poor melt stability, so that melt spinning was notapplicable thereto. Owing to the use of the novel melt-stable PTK inthis invention, melt spinning has become feasible and moreover, PTKfibers having excellent physical properties have been provided.

The PTK fibers according to this invention can be used in a wide varietyof fields in which heat resistance and strength are required.

EMBODIMENTS OF THE INVENTION

The present invention will hereinafter be described more specifically bythe following Examples, Comparative Examples and Experiments. It shouldhowever be borne in mind that the scope of the present invention is notlimited to the following Examples and Experiments.

Experiments

Synthesis Experiment 1 (Synthesis of Melt-Stable PTK)

A titanium-lined reactor was charged with 90 moles of4,4'-dichlorobenzophenone (hereinafter abbreviated as "DCBP"; product ofIhara Chemical Industry Co., Ltd.), 90 moles of hydrated sodium sulfide(water content: 53.6 wt.%; product of Sankyo Kasei Co., Ltd.) and 90 kgof N-methylpyrrolidone (hereinafter abbreviated as "NMP") (watercontent/NMP =5.0 moles/kg). After the reactor being purged with nitrogengas, the resultant mixture was heated from room temperature to 240° C.over 1.5 hours and then maintained at 240° C. for 2.5 hours. In order toapply the stabilization treatment in the final stage of thepolymerization, the reaction mixture was heated up to 260° C. over 1hour while charging under pressure a mixture composed of 9.0 moles ofDCBP, 15 kg of NMP and 75 moles of water. The resultant mixture wasmaintained further at 260° C. for 0.3 hour to react them.

The reactor was cooled, and the reaction mixture in the form of a slurrywas taken out of the reactor and was then poured into about 200 l ofacetone. The resultant polymer was precipitated, recovered byfiltration, and then washed twice with acetone and additionally twicewith water. Acetone and water were removed to obtain the polymer in awet form. The wet polymer was dried at 80° C. for 12 hours under reducedpressure, thereby obtaining Polymer P1.

When the physical properties of Polymer P1 were measured, Tm was foundto be 366° C., ΔHmc (420° C./10 min) 56 J/g, Tmc (420° C./10 min) 306°C., and the reduced viscosity 0.81 dl/g. In addition, the density (25°C.) of Polymer P1 was 1.30 g/cm³ in an amorphous form and 1.35 g/cm³ inan annealed form.

<Measurement Methods of Physical Properties>

Measurement of melting point:

With respect to the PTK thus obtained, the melting point, Tm wasmeasured as an index of its heat resistance. The measurement wasperformed in the following manner. About 10 mg of each PTK (powder) wasweighed. The sample was held at 50° C. for 5 minutes in an inert gasatmosphere and then heated up at a rate of 10° C./min so as to measureits melting point on a DSC (Model TC10A; manufactured by MettlerCompany).

Measurement of residual melt crystallization enthalpy:

With respect to the PTK obtained above, the residual meltcrystallization enthalpy, ΔHmc (420° C./10 min) was measured as an indexof its melt stability. Namely, the temperature corresponding to a peakof melt crystallization measured by the DSC is represented by Tmc (420°C./10 min) and the amount of heat converted from the area of the peakwas taken as residual melt crystallization enthalpy, ΔHmc (420° C./10min). Described specifically, about 10 mg of the PTK (powder form) wasweighed. After holding the PTK at 50° C. for 5 minutes in an inert gasatmosphere, it was heated up at a rate of 75° C./min to 420° C. and heldat that temperature for 10 minutes. While cooling down the PTK at a rateof 10° C./min, its ΔHmc (420° C./10 min) and Tmc (420° C./10 min) weremeasured.

Measurements of density and solution viscosity

The density of the PTK was measured as an index of its crystallinity ofthe PTK. Namely, the PTK (powder) was first of all placed between twopolyimide films ("Kapton", trade mark; product of E.I. du Pont deNemours & Co., Inc.). Using a hot press, it was preheated at 385° C. for2 minutes and then press-formed at 385° C. for 0.5 minute. It was thenquenched to obtain an amorphous sheet whose thickness was about 0.15 mm.A part of the amorphous sheet was used directly as a sample, while theremaining part was annealed at 280° C. for 30 minutes to use it as anannealed sample with an increased degree of crystallinity. Theirdensities were measured separately at 25° C. by means of a densitygradient tube (lithium bromide/water).

The solution viscosity (reduced viscosity, η_(red)) of the PTK was alsomeasured as an index of its molecular weight.

Namely, the PTK was dissolved in 98wt.% sulfuric acid to give a polymerconcentration of 0.5 g/dl. The viscosity of the resultant solution wasthen measured at 25° C. by means of a Ubbellohde viscometer.

Example 1 (Melt Spinning)

Under a nitrogen gas stream, the PTK polymer, P1 was charged into anextruder having a cylinder diameter of 35 mm and equipped with aspinneret which had 40 fine holes, each of 0.5 mm across. The PTKpolymer was extruded at an extrusion temperature of 375° C. and a drawdown ratio (the ratio of the take-up speed of spun fibers to thedischarge rate of the resin from the spinneret) of about 200, and thenwas cooled through a nitrogen gas environment, so that unstretchedfibers were obtained.

The unstretched fibers were stretched 3.2 times on a hot plate of 160°C. and then caused to pass for 2.5 seconds through hot air of 280° C. soas to heat set them.

The thus-obtained fibers had the following physical properties. Fiberdiameter: 20 μm. Tensile strength (23° C.): 38 Kg/mm² Tensile modulus(23° C.): 400 kg/mm² Tensile elongation (23° C.): 25%. Heat shrinkage(220° C./30 min): 7.5%. Density (25° C.): 1.36 g/cm³.

The tensile strength of the fibers was measured after they were leftover for 500 hours in an atmosphere of 220° C. It was 35.5 kg/mm².

At 250° C., their tensile strength was 20.5 kg/mm² while their tensilemodulus was 150 kg/mm².

Example 2:

Polymer P2 was obtained by conducting polymerization in the same manneras in Synthesis Experiment 1 except that 90.9 moles of DCBP was chargedinstead of 90 moles of DCBP and the reaction time at 240° C. was changedto 1.5 hours.

Example 3:

Polymer P3 was obtained by conducting polymerization in the same manneras in Synthesis Experiment 1 except that a mixture of 89.1 moles of DCBPand 0.9 mole of 2,2',4,4'-tetrachlorobenzophenone was charged instead of90 moles of DCBP.

Comparative Example 1:

Polymer CP1 was obtained by conducting polymerization in the same manneras in Synthesis Experiment 1 except that 91.8 moles of DCBP were chargedinstead of 90 moles of DCBP and that the reaction time at 240° C. waschanged to 2 hours.

Comparative Example 2

Polymer CP2 was obtained by conducting polymerization in the same manneras in Synthesis Experiment 1 except that a mixture of 85 moles of DCBPand 5.0 moles of 2,2',4,4'-tetrachlorobenzophenone was charged insteadof 90 moles of DCBP.

The individual PTKs were separately melt-spun in the same manner as inExample 1, thereby producing unstretched fibers respectively.

Physical properties of the PTKs and their processability upon meltspinning are shown in Table 1.

Those unstretched fibers were separately stretched 3.2 times on a hotplate of 160° C. and then heat set at 1.02 times in hot air of 280° C.

Physical properties of stretched yarns of Examples 2-3 are summarized inTable 2.

                                      TABLE 1                                     __________________________________________________________________________    Physical properties of PTK  Processability                                    ηred                                                                              Tm ΔHmc**                                                                       Tmc***                                                                             Density****                                                                          Melt Spinnable                                                                         Remarks                                  (dl/g)  (°C.)                                                                     (J/g)                                                                              (°C.)                                                                       (g/cm.sup.3)                                                                         properties                                                                             Polymer No.                              __________________________________________________________________________                                Drawdown took                                                                 place. Severe                                                                 fiber uneven-                                                                 ness and early                                    Comp.                                                                             0.25                                                                              366                                                                              45   285  1.35   sticking of grime                                                                      CP1                                      Ex. 1                       on spinneret,                                                                 frequent fiber                                                                breakages. Fail-                                                              ed to give unst-                                                              retched fibers.                                                               Some tendency of                                                              drawdown was                                      Ex. 2                                                                             0.40                                                                              365                                                                              50   303  1.35   observed, but                                                                          P2                                                                   spinning was                                                                  feasible.                                         Ex. 3                                                                             0.97                                                                              353                                                                              51   300  1.35   Good     P3                                       Comp.                                                                             --* 340                                                                              43   280  1.34   Poor     CP2                                      Ex. 2                                                                         __________________________________________________________________________     *Some portions were insoluble in 98 wt. % sulfuric acid.                      **(420° C./10 min).                                                    ***(420° C./10 min).                                                   ****(Annealed fibers).                                                   

                                      TABLE 2                                     __________________________________________________________________________              Physical properties of stretched fibers                                            Tensile Tensile                                                                             Tensile                                          P.P. of PTK*                                                                            Fiber                                                                              strength                                                                              elongation                                                                          modulus Density                                                                            Remarks                             η.sub.red                                                                           diameter                                                                           (kg/mm.sup.2)                                                                         (%)   (kg/mm.sup.2)                                                                         (g/cm.sup.3)                                                                       Polymer                             (dl/g)    (μm)                                                                            23° C.                                                                     250° C.                                                                    23° C.                                                                       23° C.                                                                     250° C.                                                                    25° C.                                                                      No.                                 __________________________________________________________________________    Ex. 2                                                                            0.40   20   25  13  20    280 120 1.36 P2                                  Ex. 3                                                                            0.97   20   39  20  22    370 150 1.36 P3                                  __________________________________________________________________________     *P.P.: Physical property.                                                

Example 4:

Using the facilities similar to those employed in Example 1, unstretchedfibers which had been extruded at 370° C. and spun at a draw down ratioof about 100 were stretched 5.0 times in an atmosphere of 156° C., heatset in hot air of 315° C.

The thus-obtained fibers had the following physical properties. Fiberdiameter: 23 μm. Tensile strength (23° C.): 41 Kg/mm² Tensile modulus(23° C.): 430 kg/mm². Heat shrinkage (220° C./30 min): 6.2%. Density(25° C.): 1.36 g/cm³.

The tensile strength of the fibers was measured after they were leftover for 500 hours in an atmosphere of 220° C. It was 37 kg/mm².

At 250° C., their tensile strength was 25 kg/mm² while their tensilemodulus was 160 kg/mm².

Example 5:

Under a nitrogen gas stream, the PTK polymer, P1 was charged into anextruder having a cylinder diameter of 40 mm and equipped with aspinneret which had 6 fine holes, each of diameter 1.0 mm. The PTKpolymer was extruded at an extrusion temperature of 370° C. and a drawdown ratio of 10 and then cooled in warm water of 50° C., so thatunstretched fibers were obtained.

The unstretched fibers were stretched 3.3 times in hot glycerin of 155°C., and heat set with 4% relaxation in the hot air of 300° C.

The thus-obtained fibers had the following physical properties. Fiberdiameter: 170 μm. Tensile strength (23° C.): 41 Kg/mm². Tensile modulus(23° C.): 380 kg/mm². Heat shrinkage (220° C./30 min): 6.5%. Density(25° C.): 1.36 g/cm³.

The tensile strength of the fibers was measured after they were leftover for 300 hours in an atmosphere of 220° C. It was 38.5 kg/mm².

At 250° C., their tensile strength was 17 kg/mm² while their tensilemodulus was 130 kg/mm².

Synthesis Experiment 2: (Synthesis of poly paraphenylene sulfide)

A 20 l autoclave was charged with 11.0 kg of NMP and 4.24 kg of hydratedsodium sulfide (water content: 53.98 wt.%; product of Nagao Soda K.K.)(25.0 moles as sodium sulfide). The resultant mixture was heated upgradually to 203° C. under stirring over about 2 hours in a nitrogen gasatmosphere, so that 1.59 kg of water, 1.96 kg of NMP and 0.58 mole ofhydrogen sulfide were distilled out.

After cooling down the reaction mixture to 130° C., 3.59 kg (24.42moles) of p-dichlorobenzene (p-DCB) and 3.17 kg of NMP were added. Theresultant mixture was heated at 215° C. for 8 hours for polymerization.Thereafter, 1.275 kg of water was added and in a nitrogen atmosphere,the resultant mixture was heated up to 265° C. At that temperature,polymerization was conducted for 4 hours. After cooling the reactionmixture, the resultant polymer was collected from the reaction mixtureby filtration, washed repeatedly with deionized water, and then dried at100° C. under reduced pressure.

The thus-obtained polymer was a crystalline polymer having a meltviscosity was 3,000 poises (310° C., shear rate: 1,200/sec) and amelting point, Tm of 282° C. The polymer (hereinafter abbreviated as"PPS") was melt-extruded at 330° C., thereby obtaining pellets.

Examples 6-10 & Comparative Examples 3-6:

Polymer P1 obtained above in Synthesis Experiment 1 was used as a PTK.The PTK was added with PPS obtained above in Synthesis Experiment 2,thereby obtaining a raw material for spinning.

To 100 parts by weight of Polymer Pl (PTK), the PPS obtained inSynthesis Experiment 2 were added at the proportions given in Table 3.The resultant mixtures were separately extruded at 370-380° C. intopellets.

Using those pellet samples separately as raw materials, melt spinningwas performed by the same facilities as those used in Example 1, therebyobtaining unstretched fibers.

The thus-obtained fiber samples were separately stretched 3.0 times on ahot plate and then heat set at 275° C. while maintaining their lengthconstant. Temperature conditions for the hot plate are also given inTable 3. All the the resultant fiber samples had a fiber diameter of 2μm.

Physical properties of the thus-obtained fiber samples are also shown inTable 3.

                                      TABLE 3                                     __________________________________________________________________________    Mixing ratio of                 Heat                                          polymers,   Temperature         shrinkage                                     PTK/PPS     of hot plate                                                                         Tensile strength (kg/mm.sup.2)                                                             (%)                                           (by weight) (°C.)                                                                         23° C.                                                                        250° C.                                                                      (220° C./30 min)                       __________________________________________________________________________    Ex. 1                                                                             100/0   160    38     20    7.5                                           Ex. 6                                                                             100/10  150    40     21    10                                            Ex. 7                                                                             100/20  146    37     19    11                                            Ex. 8                                                                             100/30  142    35     17    12                                            Ex. 9                                                                             100/40  138    34     17    14                                            Ex. 10                                                                            100/50  135    31     15    15                                            Comp.                                                                         Ex. 3                                                                             100/60  132    30     14    21                                            Comp.                                                                         Ex. 4                                                                             100/70  131    28     13    24                                            Comp.                                                                         Ex. 5                                                                             100/80  124    34     13    30                                            Comp.                                                                         Ex. 6                                                                             100/90  119    36     12    35                                            __________________________________________________________________________

As is apparent from Table 3, the tensile strength, especially, thetensile strength at the high temperature of 250° C. decreased and theheat shrinkage factor increased when the proportion of the PPS exceeded50 parts by weight. Accordingly, it was only possible to obtain fibersinferior in both heat resistance and strength.

In contrast, it is appreciated that the Examples of the presentinvention, in each of which the proportion of the PPS was not greaterthan 50 parts by weight, gave fibers excellent in tensile strength andheat shrinkage and featuring well-balanced heat resistance and strength.

We claim:
 1. A process for the production of poly(arylenethioether-ketone) fibers, which comprises melt-extruding a thermoplasticmaterial, which comprises:(A) 100 parts by weight of a melt-stablepoly(arylene thioether-ketone) having predominant recurring units of theformula ##STR7## wherein the --CO--and --S--are in the para position toeach other, and having the following physical properties (a)-(c):(a)melting point, Tm being 310-380° C.; (b) residual melt crystallizationenthalpy, ΔHmc (420° C./10 min) being at least 10 J/g, and meltcrystallization temperature, Tmc (420° C./10 min) being at least 210°C., wherein ΔHmc (420° C./10 min) and Tmc (420° C./10 min) aredetermined by a differential scanning calorimeter at a cooling rate of10° C./min, after the poly(arylene thioether-ketone) is held at 50° C.for 5 minutes in an inert gas atmosphere, heated to 420° C. at a rate of75° C./min and then held for 10 minutes at 420° C.; and (c) reducedviscosity being 0.3-2 dl/g as determined by viscosity measurement at 25°C. and a polymer concentration of 0.5 g/dl in 98 percent by weightsulfuric acid; and optionally, (B) up to 50 parts by weight of at leastone of thermoplastic resins at an extrusion temperature of 320-430° C.through a spinneret, stretching the resultant fibers to a draw ratio offrom 1.2:1 to 8:1 within a temperature range of 120-200° C., and thenheat setting the thus-stretched fibers at 130-370° C. for 0.1-1,000seconds.
 2. The process as claimed in claim 1, wherein the poly(arylenethioether-ketone) has a density of at least 1.34 g/cm³ at 25° C. whenannealed at 280° C. for 30 minutes.
 3. The process as claimed in claim1, wherein the poly(arylene thioether-ketone) is an uncured polymer. 4.The process as claimed in claim 1, wherein the poly(arylenethioether-ketone) is a polymer having a partially crosslinked and/orbranched structure.
 5. The process as claimed in claim 1, wherein thethermoplastic resin is a poly(arylene thioether) having predominantrecurring units of the formula ##STR8##
 6. The process as claimed inclaim 1, wherein the fibers have the following physical properties:(a)density of portions of said poly(arylene thioether-detone) being atleast 1.34 g/cm³ at 25° C.; (b) tensile strength being at least 10kg/mm² at 23° C. or at least 3 kg/mm² at 250° C.; (c) tensile modulusbeing at least 100 kg/mm² at 23° C. or at least 30 kg/mm² at 250° C.;(d) tensile elongation being at least 5% at 23° C.; and (e) heatshrinkage (220° C./30 min) being at most 20%.